Controversial trial of technology that could be used to brighten clouds is voted down in California

The city council of Alameda, California, voted early Wednesday to deny scientists permission to proceed with a controversial trial of technology that could one day be used to brighten clouds.

The project, one of the first of its kind, involved spraying salt water on the deck of a former aircraft carrier moored at a city pier. The scientists behind it planned to test devices that could create and measure aerosol plumes.

In the long term, the research could have served as a step toward a type of climate intervention known as marine cloud brightening. The concept, which is still largely theoretical, is to make clouds reflect more sunlight, which would send more heat back into space and help mitigate global warming.

Such efforts are not yet underway; rather, scientists design experiments to investigate how the technology might work. The Alameda trial would have been part of those efforts, but the City Council voted unanimously against it.

The episode has put Alameda officials at the center of a public debate that extends far beyond the city over the promises and dangers of geoengineering and whether tests of this kind of technology should continue at all. The council’s decision follows similar actions in other areas, including a state-level geoengineering ban implemented in Tennessee and the halting of a geoengineering project that Harvard scientists were trying to implement in Sweden.

However, the council’s vote was not a rejection of the science or the idea of ​​geoengineering, but rather of the researchers’ approach. Members complained that the project’s leaders had not been transparent, had not adequately informed medical professionals about its safety, and had erred in spraying salt water first and then asking for permission.

Indeed, the University of Washington scientists behind the trial had already begun their work — and had not widely publicized the details in advance — when Alameda city leaders learned more about it from reports in The New York Times and other news media. The researchers had sprayed salt water over the deck of the USS Hornet, which is now used as a museum on the Alameda waterfront. Their plan called for them to spray three times a day, on four days of the week, for 20 weeks.

But after city leaders heard about the project, they quickly shut it down to investigate its safety and hold a vote on its fate.

The idea of ​​cloud brightening is to increase the number of water droplets in clouds to increase their reflectance. Returning more sunlight to space in this way could reduce overall global warming, but would not help with other climate problems such as ocean acidification.

Geoengineering research remains a hard sell to the public despite the worsening effects of climate change, and the events in Alameda demonstrate the persistent skepticism scientists face even the most basic experiments.

Much of the council members’ deliberations avoided the larger implications of the project, focusing instead on potential local health risks — including the proximity of spray to school football fields and neighborhoods — and whether project leaders had taken the appropriate regulatory steps.

Sarah Doherty, a professor at the University of Washington who manages the cloud elucidation research program, faced pointed questions.

“I actually want you to tell us exactly what you did to us,” Councilwoman Trish Herrera Spencer said. “I think it’s a shame. I think you should all be able to tell us what you sprayed when you sprayed so we all know what we were exposed to.”

Doherty told the council the sprays contained extremely low concentrations of salt and would have little impact on the environment.

“We don’t brighten clouds. We don’t change the weather. We are not changing the climate,” Doherty said.

A consultant hired by the city similarly told the council that the project was safe and “not expected to pose an unacceptable risk to the surrounding community.”

Other council members expressed regret that they learned about the project from news reports.

‘I don’t like hearing or getting things from The New York Times. I would rather have the opportunity to review them,” said Councilor Malia Vella.

The project’s organizers, including Doherty, said in a statement that they were disappointed with the city’s decision and had begun exploring “alternative locations.” The group added that they had tried to be “completely open and transparent.”

“All experts involved confirmed the safety of the sea salt spray involved in the studies,” the scientists wrote. “These supported our own assessment that this is a safe, publicly accessible way to conduct further research into atmospheric aerosols, to support environmental goals and to promote education and equity in science.”

Alameda Mayor Marilyn Ezzy Ashcraft said the city did not need to be at the forefront of such research.

“There are so many competing considerations that we have to put into practice and I don’t think you’ve made your case,” Ashcraft told Doherty at the council meeting.

Some outside environmental organizations, meanwhile, expressed opposition to the project based on more global concerns.

More than 70 environmental groups released a statement last month urging Alameda to end the project. Opponents worried that widespread use of geoengineering technology could one day change the weather with unintended consequences or reduce the ambition of global efforts to stop using fossil fuels.

“Our real concern here is that this opens Pandora’s box,” said Mary Church, geoengineering campaign director at the Center for International Environmental Law.

Church said before the vote that her organization was not concerned about immediate impacts in Alameda, but rather that the project would lay the groundwork for widespread climate manipulation.

“It does nothing to address the root causes of the crisis,” she said.

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